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Methane Isotope Measurements in and Above the Arctic Region Aims of this work 1)Improve characterisation of the boreal wetland methane isotopic source signature – does it vary by wetland type / location / season? 2)Measure the methane source signature above the European Arctic for different air masses to calculate the isotopic signature of air arriving from different regions 3)Which scale of measurement is best for regional and global modelling of methane emissions – micro or macro? This includes a range of scales and platforms: Long-term records for background monitoring stations in the Arctic Chamber studies in wetlands Diurnal sampling of air at low levels over wetlands Collection on mobile platforms – ships, cars and planes

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Global CH 4 Sources –Isotopic Fingerprinting RHUL data unless stated. D data from Sowers (2006) Measurements made at source or within plumes coming from them Big errors on source signatures lead to even bigger errors when modelling the distribution of sources at regional or global scale

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The Keeling Plot Method Plots δ 13 C vs 1/CH 4 conc. (Usually from samples within / near a source) Assumes added methane is all from the same source and background is constant y-intercept is effectively the point where added methane = infinite concentration y-intercept = methane source signature in terms of δ 13 C

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Air samples are collected in 3 or 5L Tedlar bags using small battery operated pumps, allowing low cost air sampling. CH 4 mixing ratios are stable in the bags even if stored for several months. This provides enough air for triplicate CH 4 concentration measurements by Picarro G1301 CRDS and triplicate 13 C measurements by CF-GC-IRMS. Stainless steel or glass flasks are used for sites where CO 2, CO and H 2 measurements are also required Air Sampling for Methane Isotopic Measurements at Royal Holloway

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Lapland Road Trip (July 21-22, 2012) Moving with the airmass from NW to SE ppb increase in CH 4 associated with a 0.4 to 0.5 depletion in 13 C from the Norwegian coast 20 ppb enhancement next to wetland hotspots in Finland around Sodankyla Keeling plot for 1.5 days under the same weather system indicates that the source of this excess methane (-70 ) is wetland

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Measurements and Sample Collection on the FAAM BAE-146 Research Aircraft The aircraft is equipped with Los Gatos FGGA (FAAM) and more recently an Aerodyne QCL (Univ. Manchester) for continuous measurement of atmospheric CH4 during the flights FAAM core chemistry instrumentation rack installed in mid-cabin FGGA Pump Calibration The response time from air inlet to data screen is currently 4 seconds for the FGGA and 1 second for the QCL

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MAMM – Flight Campaigns Summer flying at 75 and 150m over wetlands in Finland and Sweden Use FGGA and QCL display to choose sample collection times Flights linked to ground-based sampling at chamber, wetland and road-trip scale

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August 2013 WAS Data (Flights B ) Combining all the flight data up to 1500m over Lapland this summer gives a single correlation suggesting that wetland is the only source for the methane increment during that campaign Compared with flight B720 (2012 wetland flight below 1500m) the source signature is the same but the error is much smaller in 2013 Source ± 0.4 (R 2 = 0.94, n = 155)

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Isotopic Signature of Methane Sources by Latitude S-SW winds N-NE winds Arctic Winter – dominated by gas leaks and heating All information gathered so far from our and North American wetland studies suggest that the signal coming from Canadian wetlands is -63 ± 3, but the signal from Scandinavian and Siberian wetlands is much lower, averaging -70 ±3. Different vegetation types in the mires might be important in this variation as the Abisko diurnal suggests. Are wetland emissions from Lapland becoming lighter? - 68 in 2008/9 to -71 in 2012/13. Check rainfall / wetland areas. Less oxidation. The only regional enriched source (-28 ) are forest fires and these are very sporadic in timing and rarely influence the isotopic signal in this region

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Which Isotopic Measurement Scale Provides the Best Data for Regional and Global Modelling? Chambers sample emissions from very small areas which target different water table and vegetation types therefore the 13 C is too variable for large scale modelling Long-term fixed site records provide a good test of the performance of models, but not data for model input Flights provide the best spatial coverage and an averaged isotopic signature for the boundary layer, but are expensive and difficult to plan to fit with the best weather conditions for emissions Cruises are rarely close to the methane source regions unless hydrate unexpectedly destabilizes A combination of road trips and diurnal sampling at source provide good regional data coverage and confirmation of the contributors to the excess CH 4